Boiler not working? Start with the safe checks
No heat from your boiler or cold radiators? Run a few safe checks below, then get a free call back to set up boiler cover for the next breakdown.
Boiler not working? Start here
A boiler not working in the middle of winter is no fun, but you're in the right place. Before you book anyone out, there are a few safe checks you can do yourself that often get the heating going again. If those don't sort it, the fault needs a Gas Safe registered engineer.
Smart Plan is a service plan, not insurance. Boiler cover is for breakdowns that happen after your plan starts, so it won't pay for a fault you already have today.
Why is my central heating not working?
Cold radiators, boiler no heat, or central heating not working at all usually comes down to one of a handful of common causes. Some you can check in a couple of minutes: a thermostat that's been knocked off, a boiler left on hot-water-only mode after summer, low pressure, or a radiator valve that's still shut. Others, like a stuck diverter valve or sludge in the system, sit inside the sealed boiler casing and need a Gas Safe registered engineer.
Smell gas or worried about carbon monoxide? Stop here
If you can smell gas, hear hissing near the boiler or pipework, or your carbon monoxide alarm is going off, don't try any checks. Turn the gas off at the meter if it's safe to, open windows, leave the property and call the National Gas Emergency line on 0800 111 999. Only go back in once you've been told it's safe.
Safe checks you can try yourself
These are the only checks a homeowner should do. Don't open the boiler casing or touch any internal parts; that's always a job for a Gas Safe registered engineer.
Quick troubleshooting checklist
| Check | What to do | Why it helps |
|---|---|---|
| Power and gas supply | Check the boiler hasn't tripped a switch at the fuse box, the plug or spur is on, and you've got credit if you're on a prepayment meter. | No power or no gas means the boiler simply can't fire. |
| Thermostat | Turn it up to about 21°C and make sure the timer or programmer is set to come on. | Heating won't fire if the set temperature is lower than the room, or the timer is off. |
| Hot water vs heating mode | Check the boiler isn't set to hot water only, a common setting left over from summer. | Many boilers can run hot water without the central heating. |
| Boiler pressure | Look at the pressure gauge. If it's below about 1 bar, top it up using the filling loop as shown in your boiler manual. | Low pressure stops hot water circulating to the radiators. |
| Radiator valves | Make sure the valves at each end of your radiators are open. | A valve turned off over summer leaves that radiator cold. |
| Reset the boiler | Press the reset button only if and as your boiler manual tells you to. | A single reset can clear a one-off lockout. |
When to stop and book an engineer
- You've run the checks above and there's still no heating.
- The boiler shows a fault or lockout code that the manual says needs an engineer.
- The boiler keeps losing pressure or needs topping up again and again.
- You've got hot water but the heating still won't come on (this can be a stuck diverter or motorised valve, which sits inside the boiler).
- There's water leaking from the boiler or pipework, or you can hear gurgling and banging from the system.
Cover for the next breakdown
If the safe checks don't fix it, switch the boiler off if it's misbehaving and use a Gas Safe registered engineer. A cover plan can't pay for a fault that is already there before the plan starts, but it can look after the next breakdown.
Already worried it'll happen again? Build cover
Smart Plan is a service plan, not insurance. You pick only the modules you want, and the boiler & central heating module covers parts and labour up to £500 if your boiler is under 7 years old, or £200 if it's over 7 years old, per 12-month period. It runs as monthly rolling cover, though once you've used a service a 12-month agreement period applies, and leaving early means paying the remaining months or 75% of the outstanding balance. A £95 call-out fee applies in set cases, such as a call-out in the first 30 days of a new plan, and call-outs run Monday to Friday, 08:00 to 18:00, unless it's an emergency breakdown.
Cover the next breakdown: get a call back
A cover plan is for the next breakdown, not a fault you already have today. Get a free call back to set up cover for next time. We aim to call you back within one working day, Monday to Friday, 08:00-18:00. It's a service plan, not insurance.
Boiler not working: common questions
Why is my boiler not working but I still have hot water?
If you've got hot water but no heating, the boiler is often set to hot water only, the thermostat or timer is off, the radiator valves are closed, or the pressure is low. Try those checks first. If they don't help, a stuck diverter or motorised valve inside the boiler may be to blame; that's a job for a Gas Safe registered engineer.
Why are my radiators cold when the heating is on?
Cold radiators usually mean a closed valve, trapped air, low boiler pressure, or sludge build-up in the system. Check the valves are open and the pressure is around 1 to 1.5 bar. If the radiators stay cold, book an engineer to look at the system.
Can I fix my boiler myself?
You can safely check the power and gas supply, the thermostat, the boiler pressure, the radiator valves, and press the reset button if your manual says to. You should never open the boiler casing or touch internal parts. Anything inside the boiler must be done by a Gas Safe registered engineer.
What should I do if I smell gas?
Don't run any checks. Turn the gas off at the meter if it's safe, open windows, leave the property, and call the National Gas Emergency line on 0800 111 999. Only return once you've been told it's safe.
Will boiler cover fix the fault I have now?
No. A fault that exists before your plan starts is not covered. Boiler cover is for breakdowns after your plan starts, with parts and labour included up to £500 if your boiler is under 7 years old, or £200 if it's older, in each 12-month period.
Why does my boiler keep losing pressure?
If the pressure drops again soon after you top it up, that usually points to a leak in the system or a faulty part such as the pressure relief valve or expansion vessel. That's not a homeowner fix, so book a Gas Safe registered engineer to find and repair the cause.
How do I set up boiler cover?
Ask for a free call back and we'll ring you to set up your plan. We aim to call you back within one working day, Monday to Friday, 08:00-18:00. Nothing is set up and no payment is taken online.
Related help and cover
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- Contact us
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A service plan, not insurance. Nothing is paid online.
Call us today
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2nd Floor, Melrose House
42 Dingwall Road
Croydon
CR0 2NE